Zoom Lens Aberration Correction via Conditional Group Movements
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Solution Overview
Problem
Conventional zoom lenses face challenges in achieving high zooming capabilities while maintaining optimal optical performance, particularly in balancing refractive powers and lens movements to correct various aberrations across different focal lengths.
Innovation Solution
A zoom lens configuration comprising five lens groups with specific refractive powers and movements, where the first, second, third, and fourth lens groups move to adjust intervals between them, adhering to conditional expressions that optimize focal lengths and displacement, ensuring effective correction of spherical aberrations, curvature of field, and coma aberrations from wide angle to telephoto end states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If zooming capability is increased by moving multiple lens groups, then focal length range is improved, but optical performance deteriorates due to uncorrected aberrations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the movement distances of lens groups and setting specific focal length ratios. Conditional expressions (1) and (2) define optimal parameter ranges for f1, f4, fw, and ft to maintain optical performance across the zoom range. This resolves the contradiction by optimizing the parameters of the moving lens groups to correct aberrations while achieving high zooming capability.
2Adaptability or versatility
If lens groups are moved to achieve zooming, then focal length variability is improved, but manufacturing precision requirements worsen due to tight conditional expressions
Solution Approach 1:
The patent defines specific parameter ranges in conditional expressions (1) and (2) that balance zooming capability with manufacturing feasibility. By setting f1/(fw×ft)1/2 within 1.80-2.80 and -f4/(fw×ft)1/2 within 0.70-1.30, the design allows for practical manufacturing tolerances while achieving high zooming performance.
3Reliability
If refractive powers of lens groups are optimized for aberration correction, then optical performance is improved, but device complexity increases due to multiple moving components
Solution Approach 1:
The patent divides the optical system into five distinct lens groups with specific refractive power assignments. The first lens group has positive refractive power, the second has negative, the third has positive, the fourth has negative, and the fifth has positive. This segmentation allows each group to be optimized for specific aberration corrections while maintaining manageable complexity through standardized movement mechanisms.
Solution Approach 2:
The moving lens groups serve multiple functions simultaneously. For example, the first lens group's movement contributes to both zooming and correction of spherical aberration and coma. The fourth lens group's movement addresses both field curvature and astigmatism while enabling focal length variation. This multi-functionality reduces the need for additional dedicated correction elements, managing overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables high zooming capabilities with satisfactory optical performance by balancing refractive powers and lens movements, effectively correcting aberrations across focal lengths, thereby enhancing imaging quality.
Implementation Method 1
a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power
Data Source
AI summary
A zoom lens comprises, in order from an object: a first lens group (G1) having a positive refractive power, a second lens group (G2) having a negative refractive power, a third lens group (G3) having a positive refractive power, a fourth lens group (G4) having a negative refractive power, and a fifth lens group (G5) having a positive refractive power, in which: intervals between adjacent lens groups change and the first lens group (G1), the second lens group (G2), the third lens group (G3), and the fourth lens group (G4) move upon zooming from a wide angle end state to a telephoto end state; and following conditional expressions are satisfied: 1.80<fl/(fw×ft)1/2<2.60; and 0.75<−f4/(fw×ft)1/2<1.20, where, fl denotes a focal length of the first lens group, f4 denotes a focal length of the fourth lens group, fw denotes a focal length of the zoom lens in the wide angle end state, and ft denotes a focal length of the zoom lens in the telephoto end state.